An amplifier circuits inductive/magnetic sensor interface can include a main signal path including one or more amplifiers configured to receive an input signal and to produce an output signal based on the input signal. The input signal may include a square-wave demodulated signal having an associated modulation frequency and an undesired frequency component at twice the modulation frequency of the square-wave demodulated signal. The amplifier circuit may include a gain feedback loop configured to set a gain of the amplifier circuit. The amplifier circuit may include a ripple reduction feedback loop configured to receive an intermediate signal on the main signal path and extract the undesired frequency component of the intermediate signal to produce a filtered version of the intermediate signal and provide the filtered version of the intermediate signal to the main signal path.
Legal claims defining the scope of protection, as filed with the USPTO.
2. The amplifier circuit of claim 1, further comprising a square wave demodulator configured to receive a sinusoidally modulated input signal and demodulate the sinusoidally modulated input signal to produce a square-wave demodulated signal for use as the input signal of the main signal path, wherein the square-wave demodulated signal includes a frequency component at twice the modulation frequency of the square-wave demodulated signal.
3. The amplifier circuit of claim 1, wherein the desired cutoff frequency is below twice the modulation frequency of the square-wave-demodulated signal.
4. The amplifier circuit of claim 1, wherein the ripple reduction feedback loop comprises an amplifier disposed between the low-pass filter and the square-wave modulator.
5. The amplifier circuit of claim 1, wherein the amplifier circuit comprises an integrated circuit.
6. The amplifier circuit of claim 1, wherein the first amplifier on the main signal path comprises a transconductance amplifier.
7. The amplifier circuit of claim 1, wherein the main signal path comprises a second amplifier.
8. The amplifier circuit of claim 7, wherein the second amplifier is disposed on the main signal path between the output and a node where the ripple reduction feedback loop receives the intermediate signal.
9. The amplifier circuit of claim 1, further comprising a pick-up coil configured to detect a magnetic field.
10. The amplifier circuit of claim 9, wherein the pick-up coil is configured to detect a reflected sinusoidally modulated magnetic field.
11. The amplifier circuit of claim 1, further comprising a processor configured to determine positional information of a moveable target from the output signal.
13. The amplifier circuit of claim 12, further comprising first and second square-wave demodulators, each configured to receive a sinusoidally modulated input signal and demodulate the sinusoidally modulated input signal to produce a square-wave-demodulated signal, wherein the square-wave demodulated signal includes a frequency component at twice the modulation frequency of the square-wave demodulated signal, and wherein the first and second square-wave demodulators are configured to provide the input signals to the main signal paths of the first and second ripple-reduction amplifier circuits, respectively.
14. The amplifier circuit of claim 13, further comprising first and second pick-up coils configured to detect a magnetic field and provide output signals to the first and second square-wave demodulators, respectively.
15. The amplifier circuit of claim 14, wherein each pick-up coil is configured to detect a reflected sinusoidally modulated magnetic field.
16. The amplifier circuit of claim 12, wherein the desired cutoff frequency is below twice the modulation frequency of the square-wave demodulated signal of the input signal of each of the first and second ripple-reduction amplifier circuits.
17. The amplifier circuit of claim 12, wherein the ripple reduction feedback loop comprises an amplifier disposed between the low-pass filter and the square-wave modulator.
18. The amplifier circuit of claim 12, wherein the amplifier circuit comprises an integrated circuit.
19. The amplifier circuit of claim 12, wherein the first amplifier on the main signal path comprises a transconductance amplifier.
20. The amplifier circuit of claim 12, wherein the main signal path comprises a second amplifier.
21. The amplifier circuit of claim 20, wherein the second amplifier is disposed on the main signal path between the output and a node at which the ripple reduction feedback loop receives the intermediate signal.
22. The amplifier circuit of claim 12, wherein the processor is configured to calculate an angle of rotation associated with a moveable target based on the first and second output signals.
23. The amplifier circuit of claim 12, wherein the processor is configured to calculate a distance associated with a moveable target based on the first and second output signals.
24. The amplifier circuit of claim 12, wherein the processor comprises a CORDIC processor.
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November 2, 2022
December 24, 2024
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